News · Google Project Zero
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Google Project Zero
Fuzzers vs. AI: Comparing Fuzzilli and BigSleep on JavaScript Engines
Summary Project Zero compared two automated tools used by Google to find vulnerabilities in Chrome’s JavaScript engine, V8, on a regular basis. Fuzzilli is a generative JavaScript engine fuzzer and BigSleep is an LLM-based bug finding system. In the past six months, BigSleep found more vulnerabilities than Fuzzilli (45 versus 37) with a 25% overlap in the specific bugs reported. Since this comparison methodology has a tendency to underestimate overlap, we also performed dedicated experiments to test theoretical overlap in vulnerabilities reported since 2023. These experiments estimated overla…
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Google Project Zero
How to fix a bug in a fix
Project Zero often works with software vendors to remediate the vulnerabilities we report and provide broader guidance on making software more secure. Some vendors express concern about potential scenarios in which they are unable to fix vulnerabilities that are causing immediate user harm, due to limitations in their patch delivery systems. Since Project Zero encounters a wide array of systems designed to protect users in the case of exceptional exploitation scenarios, both through vendor discussions and security reviews, we want to share what we’ve learned. This post provides an overview of…
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Google Project Zero
Windows Exploitation Techniques: Dangling COM Object Registrations
This short blog post is about abusing a privilege escalation bug that Microsoft recently fixed in Windows, CVE-2026-66804, that I and 14 others reported. This issue is an incomplete fix for CVE-2026-50343, a bug dubbed “Dark Elevator” by Calif. The root cause of the bug was a dangling COM object registration for the CrossDevice COM object with the CLSID {E9F83CF2-E0C0-4CA7-AF01-E90C70BEF496}. A COM registration typically needs two parts: a server executable, which for in-process components is a DLL and a CLSID entry under the HKEY_CLASSES_ROOT registry key which points to that DLL.
CVE-2026-66804, CVE-2026-50343 -
Google Project Zero
Testing race conditions with memory access tracing and stack-based delay injection
Many security bugs are race conditions, where multi-threaded execution has to occur with the right interleaving for a negative effect to appear. This creates challenges for several use cases: Confirming bug candidates that have been discovered manually or through static analysis. Regression tests: After fixing a race condition bug, there is often no good way to write a regression test that reliably triggers the bug as part of a test suite. Automatic bug discovery, such as fuzzing: It is hard for a fuzzer to exercise all interesting interleavings of concurrent operations, or reach code paths t…
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Google Project Zero
A 0-click exploit chain for the Pixel 10: When a Door Closes, a Window Opens
We recently published an exploit chain for the Google Pixel 9 that demonstrated it was possible to go from a zero-click context to root on Android in just two exploits. The Dolby 0-click vulnerability existed across all of Android, until it was patched in January 2026. While we had an exploit chain for the Pixel 9, we wanted to see if it was possible to write a similar exploit chain for Pixel 10. Updating the Dolby Exploit Altering our exploit for CVE-2025-54957 was fairly straightforward. The majority of needed changes involved updating offsets calculated for the specific version of the libr…
CVE-2025-54957 -
Google Project Zero
On the Effectiveness of Mutational Grammar Fuzzing
Mutational grammar fuzzing is a fuzzing technique in which the fuzzer uses a predefined grammar that describes the structure of the samples. When a sample gets mutated, the mutations happen in such a way that any resulting samples still adhere to the grammar rules, thus the structure of the samples gets maintained by the mutation process. In case of coverage-guided grammar fuzzing, if the resulting sample (after the mutation) triggers previously unseen code coverage, this sample is saved to the sample corpus and used as a basis for future mutations. This technique has proven capable of findin…
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Google Project Zero
Bypassing Administrator Protection by Abusing UI Access
In my last blog post I introduced the new Windows feature, Administrator Protection and how it aimed to create a secure boundary for UAC where one didn’t exist. I described one of the ways I was able to bypass the feature before it was released. In total I found 9 bypasses during my research that have now all been fixed. In this blog post I wanted to describe the root cause of 5 of those 9 issues, specifically the implementation of UI Access, how this has been a long standing problem with UAC that’s been under-appreciated, and how it’s being fixed now. A Question of Accessibility Prior to Win…
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Google Project Zero
Breaking the Sound Barrier, Part II: Exploiting CVE-2024-54529
In the first part of this series, I detailed my journey into macOS security research, which led to the discovery of a type confusion vulnerability (CVE-2024-54529) and a double-free vulnerability (CVE-2025-31235) in the coreaudiod system daemon through a process I call knowledge-driven fuzzing. While the first post focused on the process of finding the vulnerabilities, this post dives into the intricate process of exploiting the type confusion vulnerability. I’ll explain the technical details of turning a potentially exploitable crash into a working exploit: a journey filled with dead ends, c…
CVE-2024-54529, CVE-2025-31235 -
Google Project Zero
Bypassing Windows Administrator Protection
A headline feature introduced in the latest release of Windows 11, 25H2 is Administrator Protection. The goal of this feature is to replace User Account Control (UAC) with a more robust and importantly, securable system to allow a local user to access administrator privileges only when necessary. This blog post will give a brief overview of the new feature, how it works and how it’s different from UAC. I’ll then describe some of the security research I undertook while it was in the insider preview builds on Windows 11. Finally I’ll detail one of the nine separate vulnerabilities that I found…
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Google Project Zero
A 0-click exploit chain for the Pixel 9 Part 3: Where do we go from here?
While our previous two blog posts provided technical recommendations for increasing the effort required by attackers to develop 0-click exploit chains, our experience finding, reporting and exploiting these vulnerabilities highlighted some broader issues in the Android ecosystem. This post describes the problems we encountered and recommendations for improvement. Audio Attack Surface The Dolby UDC is part of the 0-click attack surface of most Android devices because of audio transcription in the Google Messages application. Incoming audio messages are transcribed before a user interacts with…
